Touch panels are used as a means for inputting characters or figures in mobile phones or personal computers. Touch panels perform signal processing of sensing a touch of a hand or a stylus pen and converting the sensed touch into an electrical signal.
When an electronic circuit is installed in a stylus pen, the stylus pen may perform a mouse function such as generating an electrical signal to select or drag a portion of an image, as well as performing a simple touch input.
When an electronic circuit is installed in a stylus pen, electric power is required to operate the electronic circuit of the stylus pen. For example, a method of installing a battery in the stylus pen and supplying electric power from the installed battery may be used.
Meanwhile, recently, a method of installing a dedicated panel for supplying power in a main body of a mobile phone and wirelessly supplying required power to the stylus pen from the dedicated panel is used.
(Patent document 1) JP 4866941 B
A power supply technique disclosed in Patent document 1 is performed by a power transmission device 4 disposed below an LCD module 3 in a smart phone. Here, the power transmission device 4 transmits electric power to a coil within a stylus pen by an induction coil. That is, in the Patent document 1, in order to supply electric power to the stylus pen, the power transmission device including the induction coil is disposed below the LCD module and electric power is transmitted and received through inductive coupling between a coil provided in the stylus pen and a coil provided in the power transmission device.
However, installation of the power transmission device including the induction coil below the LCD module to supply electric power to the stylus pen increases cost to lead to an increase in a thickness of a mobile phone.
Also, in a case in which electrode lines of a touch panel are formed of a coil, a resistance component by electrode lines of the touch panel is so great that energy is emitted as thermal energy by resistance before a circuit is resonated, causing a problem that the circuit is not resonated eventually.
In order to solve the problem, a need for a technique of supplying electric power to a stylus pen using an existing touch panel and sensing a signal received from the stylus pen, without using a separate power transmission device, has increased.